Electrofracturing is a method of dynamic fragmentation using high-voltage pulses applied to rock through a pair of electrodes. Fragmentation occurs through two general processes: 1) electrohydraulic shock and 2) internal breakdown inside bulk solid dielectrics. In the first process, electrical current is passed through water which generates a shock wave of sufficient magnitude to crush/fail the rock as the wave travels through it. In the second process, the electric current flows through the rock preferentially along mineral interfaces that then induce tensile and branching cracks at the boundary interfaces either by heating and differential expansion or by a shock wave induced by the electrical impulse itself.
Although significant research on electrofracturing of rock has been conducted, it has been limited primarily to laboratory investigations on small rock volumes (core plugs of only a few millimeters in length) at ambient stress and temperature conditions. However, prior test systems and methods cannot evaluate larger rock volumes while simulating in situ stress conditions typical of rock formations, and in particular, sedimentary reservoirs (e.g., shale gas).
The need remains, therefore, for a device and method for evaluating larger rock volumes for electrofractured characteristics while simulating in situ stress conditions typical of rock formations, and in particular, sedimentary reservoirs (e.g., shale gas).